This work was carried out to investigate the effects of several mode of picking leaves in autumn on development and harvest of branches, The results obtained are summarized ： (1) The effects of picking leaves in autumn were more conspicuous in weight of branches in length and/or size of branches. (2) In inverse propotion to the amount of picking leaves in autumn, the total weights of branches showed heavy in the non-picking leaves, the lower half part and the middle part-treatment, whereas are light in the upper half- and the all leaves picking-treatment, In spite of excessive picking leaves in autumn however, the middle part-treatment presented heavy weight of branches. (3) The yield of leaves in spring silkworm rearing, in propotion to the amount of picking leaves, were heavy in order of the non-picking leaves-, the middle part, and the lower half part-treatment, while both the upper half and the all leaves picking-treatment showed small amount of harvest. (4) The total yield of mulberry leaves and shoots of middle part-treatment, which showed the largest number of all was larger than that of the non-picking leaves and the all leave picking-treatment (leaving 5 leaves from upper part of shoot) at the ratio of 36％ and 13％, respectively.

The pathogenicity of hexagonal and tetragonal cytoplasmic polyhedron virus to one of present leading silkworm varieties, Jam 103Jam 104, and its parents, Jam 103 and Jam 104, was investigated. The activation of occult virus by oral inoculation of foreign virus as well as the interference phenomena between the activated and inoculated cytoplasmic polyhedron viruses was observed and the results obtained are as follows. 1. The pathogenicity of cytoplasmic polyhedrosis viruses. 1) There was a high significant difference in the pathogenicity of hexagonal polyhedron virus between the hybrid and its parents showing the lowest infection rate in the hybrid (Jam 103Jam 104), medium infection rate in the Japanese line (Jam 103) and the highest infection rate in the Chinese line (Jam 104). In the pathogenicityof tetragonal polyhedron virus, a significant difference was observed only between the hybrid (Jam 103Jam 104) and the Chinese line (Jam 104) by showing a higher infection rate in the Chinese line than in the hybrid. 2) The pathogenicity of both hexagonal and tetragonal polyhedron viruses showed a high significant difference in different silkworm instars inoculated by showing a higher infection rate at the second instar than at the fourth instar. 3) The pathogenicity of both hexagonal and tetragonal polyhedron viruses was increased as the concentration of viruses inoculated increased. 2. The phenomena of induction and interference by oral inoculation of foreign virus. 1) The induction rate of cytoplasmic polyhedrosis virus was higher in the parents than in the hybrid. In the parents. a higher rate in the Chinese line than in the Japanese line was observed. 2) The effect of inoculation at different instars on the induction was studied and the induction rate was higher at the second instar inoculated than at the fourth instar inoculated. 3) The degree of activation of hexagonal polyhedron virus with inoculation of tetragonal polyhedron virus was very high when a lower concentration of virus was inoculated and it was very low when a higher concentration of virus was inoculated 4) The degree of activation of tetragonal polyhedron virus with inoculation of hexagonal polyhedron virus was very low when a lower concentration of virus was inoculated and it was not observed when a higher concentration of virus was inoculated. 5) The mixed infection rate with hexagonal and tetragonal polyhedron viruses was higher at the second instar inoculated than at the fourth instar inoculated. 6) It was observed that the secondary hexagonal pc]yhedron virus activated interfered with the primary tetragonal polyhedron virus inoculated when the inoculated concentration of the primary virus is low and the primary virus inoculated interfered with the secondary virus activated when the inoculated concentration of the primary virus is high.

By means of in vitro studies, in which isolated suboesophageal of the Bombyx silkworm were cultured, it was shown that at least two Kinds of substances are biosynthesized and exert independent effects on determination of diapause or non-diapause in silkworm eggs. They are referred to as the diapause and non-diapause substance, respectively. Whether diapause or non-diapause eggs are laid may depend upon the different quality of these substances.

The function of cuticle of insect is not simply to protect the body, but to take a role to frame the body with the power of muscle. Although there are volumnous studies of silkworm, most of them are limitted to the specific time of development or particular regional studies. Some of these studies are confined to anatomical aspects. However, silkworm shows many variations at each instar or development stages, i.e. newly exuviated silkworm, gluttonous stage silkworm, etc, Therefore, the wider studies on the differentiation, spinning stage and prepupa stage as well as other subjects must be included in the study. In this line, the results of experiment are as follows： 1) Construction of cuticle at each stage of development; The construction of cuticle is different at each stage of development and each portion of the body. Wrinkles in the cuticle are disappearing as the body grows. 2) Construction of cuticle in the different portion of body; Whenever the development stage reaches gluttonous stage, the surface of body is cracked irregularly by uneveness line. The shape has appeared as if the star-like formation in the tergum region. However, it has appeared rhomb-like at the sternum. Tubercles in spotted regions appeared as if coloured granules and it is quite distinct from other regions by white colouring appearance. 3) Cuticle of thorax and intersegmental membrane; Thorax： In the middle of ecto-endo cuticle, there are coloured spots which are produced by haematoxylin. However, these spots seems to be equivalent to meso cuticle. It also seemed that these spots take certain role as if the round shaped nodules in the surface of cuticle. The entirely covered granu1ar-shape nodules is enlarged at bottom region. However, it is understood as nodules is equivalent to so-called knobs. Adbomen ： Base rising of nodules is well developed and the surface of anal-plate is flat and smooth. However, there are no spread of nodules at all. This region is seemed much thicker than other regions. Intersegmental membrane portion ： It it constructed with two layers of ecto-endo cuticles. There are no nodules in the surface and the entire surface is wrinkled irregularly.

For developing the therapeutic agents to be administered orally for treating certain silkworm diseases and applying them to clinical conditions, vehicles suitable for the agents are needed. The author presumed that Lactose, Casein, and Urea, respectively, have an effectiveness as the vehicle. A series of experiments were carried out on these substances for conforming the applicability of the vehicles at the silkworm rearing house of the College of Agriculture, at Seoul National University during the spring silkworm rearing season of 1974 and the spring and autumn seasons of 1975. The author recognized, Lactose, Casein, and Urea, when put on the mulberry leaves in a powdered form, are eaten along with the leaves by silkworm. Thus, the systemic administration of them to silkworms are possible. The author administered these individual substances orally to silkworm larvae in doses of l0mg., 30mg., 50mg., and 100mg. per gram of the body weight of the silkworm larvae at intervals of once a day, once every two days, and once every three days for 15 days. This was carried out from the first day of the fourth instar to just before mounting. The influences of these substances on the growth of silkworm larvae and the cocoons made by the larvae were observed. The author found out after completing the experiment that Lactose had no effect on growth and cocoon formation. This was observed in all cases. Casein inhibited the growth of silkworms except in the case of administered doses of once every third day in whick the growth and the cocoons were normal but the administration of the agent brought considerably large numbers of abnormal cocoons in every case. Urea inhibited both the growth and the formation of tile cocoons in most cases. For the confirmation of the clinical effectiveness as the vehicles for some therapeutic agents, the three substances, Lactose, Casein, and Urea, will be investigated more closely for the mixing amounts needed and other pertinent data.

Silkworm is known to be damaged under the unfavorable environmental conditions. Recently, it has been often argued that nicotine is a main factor to affect the silkworm nutritional balance and to result in decrease of quantitative characters, and unbalance of larval nutrition. Especially in spring season, there is tendency to produce nicotine damage to silkworm fed with the mulberry leaf near to tobacco field early cultivated in mulching system. In these connections, the trial was made in the different pots placing by the different distance 10rn, 20m, 40m, and 60m in the direction of east-north from the tobacco field. Location of pot near to the tobacco fold is 40m below the tobacco Held and gradually higher than the tobacco field by 10 degree of slope. In addition, when the mulberry field is divided into two areas from the east-south to west-north, southern east zone is lowering down below 10 degree of slope and has 36％ of east-south wind, 21％ of south-east wind and 16％ of south wind, etc. Pots are left on the mulberry field from the completion of lower part leaf harvest to just before upper part leaf harvest is completed for 32 days. Then silkworm at 4th-5th stage was fed with the leaf grown during the period and larval characters are statistically analyzed. The results are summarized as follows： 1. 10-40m distant pot statistically at the same level has the longest larval duration and 60m distant pot is. not significant at 5％ level. Whole larval duration has same tendency as in the 5th larval duration. 2. Percentage of delayed molting larvae at the 5th stage is increased in 10m distant pot and there is no significance statistically in other pots, as compared with that of control. 3. It is not showed that there is no damage to mortality of the old larvae in 60m distant pot. 4. 10-20m distant pot produces a low pupation and others are at the same level statistically at 5％ significance, 5. It is showed that nicotine damage is occurred in single cocoon freight and cocoon shell weight up to 60m distant pot, rather higher damage in cocoon shell weight than in single cocoon weight. 6. It is showed that cocoon yield from 10, 000 molted larvae including double cocoon is decreased up to 40m distant pot far from the tobacco field in which 40％ of cocoon yield in 10m distant pot by 7kg, 26％ of cocoon yield in 20m distant pot by 3.9kg, 24％ of cocoon yield in 40m distant pot by 3.6kg, and 12％ of cocoon yield in 60m distant pot by 1.8kg, as compared with control. However, there is no significance statistically at 5％ level in 60m distant pot. With these above results, it is concluded that nicotine da mage could be occurred in cocoon yield and cocoon quality up to 60m distant far from the tobacco field.

In the field of silkworm rearing industry many efforts have been made to find the chemical and physical ways which are able to save the labor in mounting procedures. In connection with these trend of the field, recently the authors developed a new mounting promoter, Boo-Choo-Ghin. Through a series of experiments we confirmed that Boo-Choo-Ghin is more effective, more convenient to use, safer and cheaper than Repper, one of the leading preparations of Japan. (The chemical composition and manufacturing method of Boo-Choo-Ghin will be published in the near future.)

The study was carried out to investigate the effects of various compositions of artificial diet for silkworms on the cocoon shell fibroin-hydrolyzing with the proteolytic enzyme. The obtained results are summarized as follows： 1. It was found that the fibroin-hydrolyzing ratio of the cocoon shell made by silkworms fed with artificial diets was lower than that of the cocoon shell made by silkworms fed with natural diet (mulberry leaf) 2. The amount of soybean meal in the artificial diet was negatively related to the sericin content of cocoon shell but it scarcely affected on the fibroin-hydrolyzing ratio. 3. The increase of sucrose in the artificial diet reduced the sericin content of cocoon shell but it didn't influence on the fibroin-hydrolyzing ratio. 4. A significant difference between male and female silkworms fed with artificial diets was found in the sericin content of cocoon shell but it was not approved in tile fibroin-hydrolyzing ratio. 5. The artificial diet containing 8 per cent of mulberry leaf powder increased the fbroin-hydrolyzing ratio more than that containing 10 per cent of mulberry leaf powder or that containing 8 per cent of mulberry leaf powder and a little of methionine did. 6. The artificial diet for all instars of silkworms increased the fibroin-hydrolyzing ratio more than the artificial diet for 1st to 3rd instars and natural diet (mulberry leaf) for the rest instars did.

This study is to investigate the content of crude protein intruded in the sericin of cocoon shell and pupa by treatment of buffer solution (pH 1 to pH 13) 20 ml per 1 gram for 30 and 60 minutes at 30, 60 and 1002, respectively. The results obtained are summarized as follows. 1. The quantity of total crude protein obtained from cocoon shell and pupa by treatment during 30 minutes at 30 was dissolved as the largest quantity of 11.874 mg/g at pH 1 and l5.93mg/g at pH 13, but dissolved the smallest quantity 1.75g/g at pH 5 as known. and tile quantity of crude protein treated for 60 minutes is 13.437mg/g at pH 1 and 22.50mg/g at pH 13. Also, the smallest quantity is 2. 813mg/g at pH 5 as known. 2. By the treatment during 30 minutes at 60, the dissolved largest quantity was 13.12mg/g at pH 1 and 21.875 mg/g at pH 13, but the smallest quantity is 2.375mg/g at pH 5 as known After treatment for 60 minutes at 60, the dissolved largest quantity was 17.500 mg/g at pH 1 and 31.56mg/g at pH 13, bu the smallest quantity is 3.849 mg/g at pH 5. 3. The dissolved crude protein from the cocoon shell and pupa by treatment for 30 minutes at 1002 was the largest quantity of 147.000mg/g at pH 1 and 398. 125mg/g at pH 13, but the smallest quantity is 75.00mg/g at pH 5 as known. After treatment for 60 minutes at 1002, the largest quantity was 253.76 mg/g at pH 1 and 460.625mg/g at pH 13, but the smallest quantity is 139.375mg/g at pH 5 as known. 4. The dissolved crude protein from the cocoon shell and pupa was not different in quantity by treatment at 30 or 60. But dissolved crude protein was large quantity from cocoon shell more than pupa, as known. 5. The treatment of cocoon shell and pupa during 60 minutes at 10020 was increased to the dissolved largest quantity of crude protein of 19.20％ at pH 1 and 22. 18％ at pH 13 from the cocoon shell and 6. 12％ at pH, an d 23.87％ at pH 13 from the pupa. But dissolved crude protein was increased to the larger quantity from pupa more than cocoon shell.

This experiment was conducted to study the reasonable deguming method of cocoon on the Boss silk making. The results obtained are as follows： 1. Reasonable deguming method of cocoon on the floss silk making was observed to be about 0.75％ NaSiO, 2％ NaCO solution during 40 minutes boiling Process. 2. Treatment 6 increased qualities of floss silk and hand spun silk as compared with the other conventional method.